A production log is a well log run in a production or injection well. Small diameter tools are used so that they can be lowered through tubing. In the past, well production services and devices included continuous flow meter, packer flow meter, gradiomanometer, manometer, densimeter, water cut meter, thermometer, radioactive-tracer logs, temperature logs, calipers, casing collar locator, fluid sampler, water entry survey, etc.
A well log can be a wireline borehole log. The product of a survey operation, also called a survey, consisting of one or more curves. Provides a permanent record of one or more physical measurements as a function of depth in a well bore. Well logs are used to identify and correlate underground rocks, and to determine the mineralogy and physical properties of potential reservoir rocks and the nature of the fluids they contain. A well log is recorded during a survey operation in which a sonde is lowered into the well bore by a survey cable.
The measurement made by the downhole instrument will be of a physical nature (i.e., electrical, acoustical, nuclear, thermal, dimensional, etc.) pertaining to some part of the wellbore environment or the well bore itself. Other types of well logs are made of data collected at the surface; examples are core logs, drilling-time logs, mud sample logs, hydrocarbon well logs, etc. Still other logs show quantities calculated from other measurements; examples are movable oil plots, computed logs. etc.